In recent years, expected has been wider use of a “PET-MRI device” that is a combination of a positron emission tomography device (PET device) and a magnetic resonance imaging device (MRI device). For example, the PET-MRI device is expected to be used for early diagnosis of Alzheimer's disease. Conventionally, in image capturing by the MRI device, known has been a fact that strain is generated on an MR image due to non-uniformity of a magnetostatic field.